Solvent treating of mineral oils



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SOLVENT TREATING OF MINERAL OILS Fmr-3d Aug. 26, 1959 2 Sheets-Sheet 1 jEL ,Mw .nM/m u@ 1/ "SO/ VENT st-PARA Tom b DIO 1105 SEPARATOR inmensa5577 LEE doo/.512km mm m* "imam/Na: 577m.

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SOLVENT TREATING OF MINERAL OILS VFiled Aug. 26, 1959 2 Sheets-Sheet 2.SEPA 72A Tcl-z2 :SOLL/NT Imm' .SETJAzzA-ron FEEP OIL /IVLET 63 Z9]SSETTLEN. L-P.. 77

H5/vw- Qekovfirey COLD STAGE J/ Patented June 17, 1941 SOI-.WENT"liItEATING 0F MlNER/AL (MLS Charles 'S. Lynch, Fanwood, N. J., assignerto Standard Oil Development Company, a corporation of DelawareApplication August 26, 1939, Serial N o. 29254145 'l Claims. (Cl.Hifi-13) The present invention relates to the segregation of mineraloils into their relatively more aromatic 'fractions `and into `theirrelatively more parailinic fractions. The invention especially relatesto a solvent treating system in which the selective Sol'- vent afterseparation of vthe `respective phases is Arecovered Without thenecessity lof distillation. In accordance with the present invention therev covery of the solvent from the raiiinate phase and from `the solventextract phase is accomplished "by forming a salt of said solvent,subjecting the phase to conditions adapted to secure the formation of an`aqueous solvent salt `layer and an oil layer, `separating the oil andrecovering the solvent `from the ysolvent salt layer by reacting thereadily .decomposable salt.

lt is well 'known in the art to treat oils, particularly petroleum oils,with various solvents in order to separate these oils into theirrelatively more aromatic or hydrogen poor constituents and into theirrelatively more param-nic or hydrogen rich constitutents. In theseprocesses solvents of the class having -a preferential selectivity forthe aromatic constituents are usually employed. Sol

vents of this class are, for example, phenol, f-urtural, sul-furdioxide, cresol, nitrobenzene, aniline, beta beta dichlor dieth-yl etherand the like. The solvent and the `oil are contacted by various means,as for example, `by a batch or multi-batch process. However, in general,the usual procedure is to contact the solvent and the Aoil in a.countercurrent tower treating operation. In this operation the lighterphase, usually ythe oil, is introduced atthe `middle or bottom sectionof the tower, while the heavier phase, usually the solvent, isintroduced atthe upper part of the tower. The respective phases iiowcountercurrently under conditions to secure a maximum contact betweenthe solvent `and the oil. Contact between the countercurrently flowingphases is usually secured by suitable distributing and contacting means,as for example, packed masses, pierced plates, distributing trays, andthe like. Temperature and pressure conditions on the tower are adjusted.to secure the formation of a solvent poor or raffinate phase, the oil ofwhich is highly parafflini-c in nature, and a solvent rich or solventextract phase, the oil of which is highly aromatic in character. `Therespective phases `are separated and handled in a manner to remove thesolvent from the extract and the raffinate. This is usually accomplishedby a distillation process, providing a .suiicient differential existsbetween the boiling points .of the solvent and the oil.

Other means are also employed, as for example,

by re-extraction with a secondary solvent or by Washing with water andthe like. In these solvent treating processes the removal of the solventfrom the respective phases in an efficient and economical mannerpresents a major problem. It is extremely desirable that the solvent befully recovered and that the last traces of the solvent be removed fromthe oil. When operating 'in this manner a large part of the cost `of theentire solvent treating operation is in the recovery of the selectivesolvent. I have now discovered an improved solvent treating operation inwhich the selective solvent maybe readily removed from the oil in anefficient and economical manner.

The process of my invention may be fully understood by reference to theattached drawings which are given for the purpose of illustration andshould not be construed as limiting the invention in any mannerwhatsoever. For purposes of illustration it is assumed that theselective solvent is phenol. Figures 1 and 2 illustrate similarprocesses with the exception that in Figure 1 the phenol and phenolatesalts are separated prior to decomposition of the phenolates andregeneration of the phenol.

Referring specifically to Figure l, a feed oil, which for the purpose ciillustration is taken a petroleum lubricating oil having a gravity ofabout 25 A. P. I. and a viscosity of about Ll/ii) sec. Saybolt at 100F., is introduced into countercurrent solvent treating tower I by meansof feed line 2. The selective solvent, which for the purpose ofillustration is taken to be phenol, is introduced into counter-currentsolvent treating tower I by means of solvent feed line 3. The solventand the oil i'iow counter-currently under conditions adapted to securethe formation of a raffinate phase which is removed from tower l bymeans of line l and a solvent extract phase which is removed from tov/erl by means of line 5. The selectivity and the solvent power of thesolvent may be modilied by the introduction of a solvent modifying agentinto tower I by means of lines 6, l, and 8 respectively. solventmodifying agent is preferably water or phenolic water, although othersubstances such as glycols, alcohols, and liqueed normally gaseoushydrocarbons may be used. The raffinate phase after removal from tower lis preferably cooled in cooler 9 andl then introduced into separator l tin which phase separation occurs. The less parafnic phase relativelyrich in solvent is separated from the more parafnic phase by means ofline Il and may be introduced into tower l. Phase separation inseparator I may be facilitated by the introduction of water or a similaragent by means of line I2. The more parafllnic phase relatively poor insolvent is removed from separator it? by means of line I3 and introducedinto solvent separator I4 which may be a still or steam stripper.Solvent is removed from solvent separator` I4 by means of line I5 andmay be recycled to line 3. A solvent free raiinate highly paraffmic innature is removed from solvent separator ifi by means of line I6. Theextract phase withdrawn by means of line 5 may be cooled in cooler l1and then introduced into separator ES in which a phase separationoccurs. rlhe relatively less aromatic oil fraction may be withdrawn fromseparator i8 and returned to tower I by means of line I9. PhaseSeparation may be facilitated by the introduction oi water into thesolvent extract phase by means of line 20. The more highly aromaticfraction dissolved in the solvent phase is withdrawn from separator I8by means of line 2|, mixed with an alkaline carbonate solution which isintroduced by means of line 23, heated in heater M, and then introducedinto an initial solvent recovery stage 22. For the purpose ofillustration, the alkaline carbonate solution is assumed to be sodiumcarbonate. The sodium carbonate is introduced into mixer and heater I4by means of line 23. Carbon dioxide is removed from the initial (solventrecovery) stage 22 by means of line 2i and passed into carbon dioxidestorage 25. A mixture of oil, water, sodium phenolate, and phenol iswithdrawn from initial stage 22 by means of line 26 and introduced intosettler 21. Settler 21 is maintained at approximately the sametemperature and pressure as initial stage 22. In settler 21 an oil phasesubstantially free oi water and solvent forms. This oil phase iswithdrawn from settler 21 by means of line 28, and may be subsequentlystripped with steam to remove the last traces of phenol. The phenoldissolved in an aqueous phenolate solution is withdrawn from settler 21by means of line 29, cooled in cooler l5 and then introduced into asecondary stage 30, the temperature of which is in the range from about'75 to 100 F. below the temperature existing in initial stage 22. Underthese conditions a phase separation occurs comprising a phenol phasesubstantially free of water and an aqueous phenolate phase. The phenollayer is withdrawn from secondary stage 30 by means of line 3i andintroduced into drying still 32 in which the last traces of water areremoved overhead by means of line 33. Substantially anhydrous phenol iswithdrawn from unit 32 by means of line 34 and recycled to line 3. Theaqueous phenolate phase formed in secondary stage 30 is withdrawn fromsaid stage by means of line 35 and introduced into a phenol recoverystage 3%. In this stage the phenolates are converted into correspondingphenols by treatment with carbon dioxide which is introduced from carbondioxide storage 25 by means of line 31. The mixture consisting of phenolsodium carbonate solution is removed from phenol recovery stage 36 bymeans of line 33 and introduced into settler 3Q. Phenol is removed fromsettler 39 by means of line 30 and introduced into phenol line 3i. Thecarbonate solution is removed from settler 39 by means of line 4I. Thewater removed from drying unit 32 by means of line 33 is introduced intothe carbonate solution removed by means of line di. The aqueouscarbonate solution is recycled by means of line 23. Fresh carbonatesolution may be introduced into the system by means of line i2 whilefresh phenol may be introduced into the system by means of line t3.

Referring specifically to Figure 2, feed oil. which is taken as apetroleum lubricating oil having a gravity of about 25 A, P, I. and aviscosity of about 440 sec. Saybolt at 100 F., is introduced intosolvent treating tower 50 by means of line 5I. A selective solvent,which for the purpose of illustration is taken to be phenol, isintroduced into tower 50 by means of line 52. These phases flowcountercurrently under conditions adapted to secure the formation of arafnate phase and the formation of a solvent extract phase. Theselectivity and the solvent power of the solvent may be modified oradjusted by the introduction of a solvent modifying agent, as forexample, water into tower 50 by means of lines 53, 56, and 55respectively. The raiinate phase is withdrawn from tower 50 by means ofline 81. This phase may be cooled in cooler 55 and then introduced intor-ainate separator 51. The less parainic phase containing `a relativelylarge amount of solvent may be removed from separator 51 by means ofline 58 and introduced into solvent treating tower 50 or withdrawn bymeans of line 88. The more parafnic phase is removed from separator 51by means of line 59 and introduced into solvent separator 6U which maybe a still or stripping unit. The solvent is removed from solventseparator 69 by means of line 6I, while the solvent-free raffinate isremoved by means of line '52. The solvent extract is removed from tower`Il!) by means of line 63 and may be cooled in cooler S4 and thenintroduced into separator E5. The more parafinic phase may be removedfrom separator 65 and introduced into tower 50 by means of line 65. Themore aromatic fraction is mixed with an alkaline carbonate solutionwhich is introduced by means of line 5S, heated in heater 89, and thenintroduced into initial solvent recovery stage 51 of a solvent recoveryunit. For purposes of illustration, the alkaline carbonate solution isassumed to be sodium carbonate. Carbon dioxide is removed 'from initialstage 61 by means of line 1|] and introduced into carbon dioxide storage1I. The extract solution consisting of oil and phenol dissolved inaqueous sodium phenolate is removed from initial stage 61 by means ofline 12 and introduced into a settler 13 maintained at a temperaturesubstantially equivalent lto the temperature of stage 01. An oil phasesubstantially free of solvent and water forms in settler 13 and isremoved by means of line 1li. rIhe oil free aqueous solution of phenoland phenolates is withdrawn from settler 13 by means of line 15. iscooled in cooler S0 to about 100 F. below the temperature in settler 13and is introduced into a phenol recovery stage 1S. The sodium phenolatesare decomposed in phenol recovery stage 16 by means of carbon dioxidewhich is removed from carbon clioxide storage 1I and introduced intostage 15 by means of line 11. The mixture of phenol, water, and sodiumcarbonate solution is withdrawn from stage 16 by means of line 18 andintroduced into settler 'I9 in which a sodium carbonate solution phaseand a phenol phase form. Sodium carbonate solution is withdrawn fromsettler 19 by means of line and recycled to line 69. Phenol is removedfrom settler 19 by means of line BI and introduced into still 82 inwhich the last traces of water are removed therefrom. The

` initial solvent recovery stage.

water lis removed `from still 8.2 by means of line 8'3 and introducedinto 'the sodi-um carbon-ate solution removed from `settler "lll` bymeans of line .820. Phenol substantially tree of water is removed fromstill 182 by means of line -84 and reu cycled to line 52. Fresh phenolmay be introduced into the system by means of Iline 85, while freshsodium carbonate may be introduced *into the system by means of `line36.

The process of the present invention may be widely varied. The process:may be applied in the recovery of solvents used in the treatment ofpetroleum oils boil-ing in the lubricating, heavy naphtha, or lightnaphtha range., The invention is particularly applicable in the recoveryof phenolic type solvents, 4as for example, oresol, phenol, and otherweakly acidic reacting solvents. The invention, however, is particularlyapplicable in the recovery of mono-hydroxy phenol.

The temperature and pressure conditions maintained in the solventtreating tower will depend upon the particular `solvent being employed,the oil `being treated, and upon the yield and quality of productsdesired. In general, yatmospheric pressures are employed and -atemperature in the range between the melting point of the solvent andthe temperature at which complete miscibility occurs between the solventand the oil. Preferred conditi-ons are such that a temperature of about200 F. or higher is maintained at the point at which the solvent extractphase is withdrawn ,from the system. The extent to which the solventextract phase is chilled to secure the separation of a relatively moreparanic fraction will `depend upon the amount of oil it is desired toprecipitate and may be varied considerably. However, it is preferredthat the temperature of the solvent `extract in the initial Istage inwhich the extract contacts the carbonate solution should be in the rangefrom about `150" F. to 225 F., preferably in the range of about 2,12 F.Although under certain conditions it may be desirable to employ excesspressures, ,in general it is preferred to employ .atmospheric pressure,The temperature in the ysettler should be substantially equivalent tothe temperature maintained in the The temperature in the phenol recoverystage of the solvent recovery system is, preferably maintained in thereliefs from about 50 to 1.0.0a below `the temperature maintained in theinitial stage. The pressure main te ined in said tertiary or phenolatedecomposition stagle may vary from about l to 50 atmospheres, dependingupon the temperature employed and is preferably in the range not over 10atmospheres.

Althoueh any water soluble carbonate may be contacted with the solventextract in the initial stage of the solvent recovery system, it isoreferred to employ alkali carbonate such as sodium and potassiumcarbonate. The Quantity of can bonate used vis preferably aqueoussolution comprising 10 to 30% carbonate in an amount sufficient tosecure the conversion of about 20 to 39% of the solvent to the valkaliohenolates. I have found that an aqueous solution of approximately 25%phenolates will substantially dissolve all the remaining phenol andcause the separation oi' a solvent free oil.

Under certain operations in which water is added to the solvent extractphase in order to cause precipitation of a relatively highly parafnicoil, I have folmd: it preferable to add a small amount of the salt ofthe present invention to the EXAlWPLE 1 Various amounts of sodiumcarbonate were added to water used in washing spent phenol from solventextracts. The operations were conducted under uniform .conditions withthe following results:

TABLE 1 Percent Volume of oil NazGOa separating in Pcenltlll in solu- 15minutes at p in?? FY tion 200 F. a

EXAMPLE 2 A material balance further illustrating the present inventionis as follows:

Solvent treating tower (Volumes) Feed Withdrawn Oil Solvent WaterRaflinate Extract leed feed injected phase phase Oil 74 26 Phenol 200 l18 183 Water 10 10 10o 200' 11 92 21o Total 311 811 Initial stage andsettler Feed Withdrawn 25 percent Phenol l Exlggt sodium Extract aqueous'iaorxbn p `carbonate salt phase l' e Oil 2G 26 Phenol 183 Trace 138lhenolatc..Y 45 Water l0 10.0 110 219 1D0 26 293 TotaL 319 319 Secondarystage Feed Withdrawn Phenol Aqueous aqueous phenoL Phenol salt phase atc293 140 153 Total 293 293 Tertiary Stage and settler Feed WithdrawnAqueous carbona e phase Carbon dioxide Phenol phase A qucous phenolatcPhenoL...

rPhe process of the present invention is not to he limited by any theoryor mode of operation, out only by the following claims in which it isdesired to claim all novelty insofar as the prior art permits.

I claim:

l. Solvent treating process comprising contacting a petroleum oil with aphenol solvent under conditions adapted to secure the formation oi araiilnate phase and a solvent extract phase, separating the solventextract phase and mixing the same with an aqueous alkali metal carbonatesolution under conditions to convert a portion of the phenol to thecorresponding alkali metal f.

phenclate and to secure the formation of an extract phase substantiallyfree of phenol and phenolates, and an aqueous phenol phenolate phasesubstantially free of extract, separatingr the extract phase from theaqueous phenolatephenol phase, cooling the latter phase to separate aphenol phase from an aqueous phenolate phase, treating the aqueousphenolate phase with carbon dioxide to convert the phenolate to thecorresponding phenol.

2. Process in accordance with claim 1 in which said solvent ismonohydroxy phenol and in which said aqueous alkali metal carbonatesolution is sodium carbonate solution.

3. Process in accordance with claim 1 in which approximately 20 to 30%of the phenol is converted to the corresponding alkali metal phenolate.

fl. Solvent treating process comprising treating a petroleum oil withphenol under conditions to form a solvent extract phase and a rainnatephase, removing the solvent extract and treating the same in an initialstage with an aqueous sodium carbonate solution under conditions toconvert approximately 20 to 30% of the phenol in said phase to thecorresponding phenolate and to secure the formation of a substantiallypure extract layer and the formation of an aqueous phenolate phenolphase substantially free of extract, separating the extract from theaqueous phenolate-phcnol phase, cooling said latter phase in a secondarystage to secure the formation of a phenol phase and an aqueous phenolatephase, subjecting said aqueous phenolate phase to treatment in atertiary stage with carbon dioxide evolved from said initial stage underconditions to convert the phenolate to the corresponding phenol,combining the phenol from the secondary stage and the phenol from thetertiary stage and recycling the same to the process.

5. Process for the removal oi phenol from solvent extracts secured inthe solvent treatment of petroleum oils` comprising contacting saidsolvent extract in an initial stage with a sodium carbonate solution ata temperature in the range of about 150 F. to 225 F. under conditions toconvert approximately 20% to 30% of the phenol to the correspondingphenolate, removing carbon dioxide therefrom, passing the liquidproducts from said initial stage to a secondary stage and maintainingthe temperature in the secondary stage substantially equivalent to thetemperature in said initial stage whereby an oil layer substantiallyfree of phenol and phenolates and an aqueous phenol-phenolate salt phasesubstantially free of oil are formed, removing the oil phase, coolingthe aqueous phenolphenolate salt solution phase in a tertiary stagewhereby a phenol layer and a phenolate salt solution layer form,separating the phenolate layer and regenerating the corresponding phenolfrom said phenolate solution phenol stage by contacting with said carbondioxide removed from said initial stage, combining the phenol from saidtertiary stage and said nal stage, and recycling the same to theprocess.

6. Process in accordance with claim 5 in which the aqueousphenol-phenolate salt phase is cooled 75 to 100 F. below the temperaturemaintained in said initial stage.

'7. Solvent treating process comprising countercurrently contacting apetroleum oil with phenol under conditions to form a raiiinate and asolvent extract phase, separating said solvent extract phase and addingthereto an equivalent volume of a 2% to 4% sodium carbonate solutionwhereby an oil phase and an aqueous sodium carbonate solvent extractphase form, separating said latter phase, contacting said latter phasewith additional quantities of sodium carbonate solution at a temperaturein the range of about 150 F. to 225 F. under conditions to form asubstantially pure oil phase and an aqueous phenol phenolate phase,removing carbon dioxide therefrom, maintaining the temperature in thisrange and removing the resulting oil phase from the aqueousphenol-phenolate solution phase, cooling the aqueous phenol-phenolatesolution phase from about 75 to 100 F. whereby a phenol layer and aphenolate solution layer form, separating the phenolate layer andregenerating the corresponding phenol from said phenolate layer bycontacting with said carbon dioxide, separating the regenerated phenol,combining the respective phenol streams and recycling the same to thesystem.

CHARLES S. LYNCH.

